Better on DVD: The 2015 adaptation by Hiromu Arakawa is best appreciated by watching in one go, especially since certain episodes involve more dialogues and plotting and less action.
Crowning Music of Awesome: Both openings of the 2015 adaptation, made by Uverworld and Nico Touches the Walls. The endings by Eir Aoi and Kalafina, by comparison, are purely epic.
Fanon Discontinuity: The last two episodes of the OVA are often regarded a being this, for having significantly lower production values than the previous four.
Fridge Brilliance: During the duel against Bahadur, Daryun chose the sword instead of his Weapon of Choice, the spear. However, a sword would be more useful and convenient in a close combat fight, even when broken, as seen when Daryun used the broken sword to stab Bahadur.
Germans Love David Hasselhoff: Overlapping with Mexicans Love Speedy Gonzales, the 2015 adaptation has garnered a small but strong fanbase in Iran, of which inspired the original novels. This is especially noteworthy in that downloading a single anime episode there - let alone an entire series - takes a great deal of time and bandwidth. More about it can be read here.
Ho Yay: Daryun and Arslan have quite a few moments, especially in the early OVAs, and their relationship could be easily interpreted as a sort of Bodyguard Crush. There's also Daryun and Narsus who used to be best friends before Narsus was expelled from the court, and now play Vitriolic Best Buds to each other.
It doesn't help (or does, depending on your point of view...) that many of anime character designer Sachiko Kamimura's fantasy characters look exactly the same as her Arslan characters, down to their costumes... and she's done a number of BL novel illustrations. At one point she actually had to clarify at her website that the couple in a picture are, despite all appearances, not Daryun and Arslan. (She wasn't very convincing.)
Launcher of a Thousand Ships: Arslan, there's Daryun x Arslan, Elam x Arslan, Etoile x Arslan, Narsus x Arslan, Rajendra x Arslan, and others.
In episode 12, when Daryun saves Arslan from death at the hands of a sorcerer, he suddenly increases his speed in a way that makes it look like he is running in fast motion. The fact that when he does this, Daryun also totally destroys all the people in his way makes the scene (which was supposed to be serious) comical.
Episode 24 gave us an Imperial Stormtrooper Marksmanship Academy moment that's almost impossible to take seriously where upon entering the castle, Arslan's group is showered upon by a unit of Lusitanian archers...only for Farangis to walk into the raining arrows, and not get hit due to her "divine protection."
Values Dissonance: One of an In-Universe variety: (1) Lusitania's religious war against other nations is the main source conflict within the continent of the story; (2) Arslan struggles against his own country's tradition of slavery; (3) Etoile is a good person despite the religious bigotry; and (4) Gieve hates mindless servitude, while Elam actually wants to work for Narsus. Narsus sums it all up rather nicely in a speech suggesting how morals are like the multitude of stars within the universe, numerous and trying to outshine each other.